M35053 Datasheet, PDF (27/47 Pages) Mitsubishi Electric Semiconductor – SCREEN CHARACTER and PATTERN DISPLAY CONTROLLERS

MITSUBISHI MICROCOMPUTERS
M35053-XXXSP/FP
SCREEN CHARACTER and PATTERN DISPLAY CONTROLLERS
(2) Before setting registers at the starting of system, be sure to reset
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the M35052-XXXSP/FP by applying “L” level to the AC pin.
(3) Power supply noise
When power supply noise is generated, the internal oscillator cir-
cuit does not stabilize, whereby causing horizontal jitters across
the picture display. Therefore, connect a bypass capacitor be-
tween the power supply and GND.
(4) Synchronous correction action
When switching channel or in the special playback mode (quick
playback, rewinding, and so on) of VTR, effect of synchronous
correction becomes strong, and distortion of a character is apt to
occur because the continuity of video signal is suddenly switched.
When the continuity of video signal is out of order, erasure of
displayed characters is recommended in a extreme short time to
raise the quality of displayed characters.
(5) Notes on fSC signal input
This IC amplifies the subcarrier frequency (fSC) signal (NTSC, M-
PAL system: 3.58MHz, PAL system: 4.43MHz) input to the OSCIN
pin (17-pin) and generates the composite video signal internally.
The amplified fSC signal can be destabilized in the following cases.
a) When the fSC signal is outside of recommended operating con-
ditions.
b) When the waveform of the fSC signal is distorted.
c) When DC level in the fSC waveform fluctuates.
When the amplified signal is unstable, the composite video
signal generated inside the IC is also unstable in terms of syn-
chronization with the subcarrier and phase.
Consequently, this results in color flicker and lost synchroniza-
tion when the composite video signal is generated. Make note
of the fact that this may prevent a stable blue background from
being formed.
(6) Forbidding to stop entering the fSC signal
This IC doesn’t properly work if the fSC signal is not entered into
the OSCIN pin (pin 17), so don’t stop the fSC signal so as to work
the IC. To stop the IC, turn the display off (set 0 in the register
DSPON (address F816).)
(7) Forbidding to set data during the period in which the internal
oscillation circuit stabilizes
a) To start entering the fSC signal when its input is stopped.
b) To start oscillating the oscillation circuit for display when its
oscillation is stopped. (to assign “1” to the register STOP1 (ad-
dress F816) when it is assigned “0”, or the like.)
c) To turn on the internal bias when it is turned off. (to assign “1”
to the register LEVEL1 (address F816) when it is assigned “0”.)
There can be instances in which data are not properly set in the
registers until the internal oscillation circuit stabilizes, so follow
the steps in sequence as given below.
1) Set “0” in the register DSPON (address F816). (the display is turned
off)
2) Effect the settings a), b), and c) given above.
3) Wait 20 ms (the period necessary for the internal oscillation cir-
cuit to stabilize) before entering data.
4) Set necessary data in other registers, and make the display RAM
ready.
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